The present invention relates to a rotation detector that is attached to a hub of a front wheel of a two-wheeled vehicle, such as a motorcycle, a bicycle and so on, and transmits the rotation number of a wheel of the two-wheeled vehicle to a indicator such as a speed meter and so on.
As an existing electric rotation detector, there is one such as disclosed in Japanese Patent Laid-Open No. 264817/1990. When such the rotation detector is used as a rotation detector for use in a two-wheeled vehicle (for instance, a motorcycle), the rotation detector is formed by disposing a magnetic detecting element (Hall IC) and a magnet, both of which are mounted on a circuit board, to a substantially cylindrical resin case having a detection surface for detecting a detecting object so as to follow the detection surface, and followed by sealing the circuit board, the magnetic converting element and the magnet with a sealing member made of an epoxy resin and so on. It is general for the rotation detector to be attached to a mission case or a sprocket cover and to detect, as a detecting object, a mission gear, a tooth point of the sprocket or the like revolving therein.
When a tooth point of a mission gear or sprocket or the like is detected with such the rotation detector as a detecting object, since there is a little clearance in the detecting object, the object is caused to vibrate owing to a body stiffness, an engine displacement or the like of a vehicle (two-wheeled vehicle), and a detection position gap between the detecting object and the rotation detector may result in fluctuating. This generates a magnetic fluctuation in the rotation detector and resultantly becomes detection noise. Accordingly, there is a problem in that an indicator for displaying, for instance, a speed corresponding to an output data that is output from the rotation detector may wrongly operate.
The present inventors paid attention to the above problem and have proposed, as shown in Japanese Patent Laid-Open No. 229714/1997, an electric rotation detector that can be attached to a hub of a front wheel of a two-wheeled vehicle. The rotation detector is provided to a resin housing with an insertion portion through which an axle (front axle) of a two-wheeled vehicle is inserted, is equipped to the insertion portion with a rotor having a plurality of magnetic poles that rotates synchronously with a wheel fitted to the axle, and detects the rotation of the rotor by means of a magnetic detecting portion that is accommodated in the housing and made of such as Hall IC or the like. The rotation detector, without incurring an adverse influence of the detection noise due to the vibration of the detecting object, allows accurately detecting the rotation.
In recent years, demands for the cost reduction of the rotation detectors that are applied to the two-wheeled vehicles are increasing. Accordingly, there is a tendency in which the rotation detecting portions are switched from the magnetic detecting elements such as Hall ICs and so on to cheaper magnetic responsive elements such as reed switches or the like. However, there is a problem in the magnetic detecting means using the magnetic responsive element in that from it characteristics and structure, in comparison with the magnetic detecting portion that uses the Hall IC or the like, vibration resistance is low.
The invention is carried out by paying attention to the aforementioned problem and intends to provide a rotation detector that is excellent in the vibration resistance even when the cheaper magnetic responsive element is used in the magnetic detecting portion.
In the invention, in order to overcome the aforementioned problem, a rotation detector comprises a housing provided with a tubular insertion portion through which an axle is inserted; a rotor that is provided with a cylindrical portion through which the insertion portion is inserted and has a plurality of magnetic poles, and rotates synchronously with a wheel that is fitted to the axle; a rotation detecting portion for detecting a change of the magnetic poles accompanying the rotation of the cylindrical portion; and a magnetic member that is disposed in the surroundings of the insertion portion of a bottom of the housing and can hold the rotor to the bottom when the cylindrical portion is fitted into the insertion portion.
In addition, the magnetic member is formed of a plane table member disposed so as to surround the insertion portion in the bottom portion of the housing.
Furthermore, the magnetic member is formed integrally with the insertion portion.
Still furthermore, a rotation detector comprises a housing one end of which abuts against an inner wheel of a bearing that is disposed to a hub of a wheel, and which is provided with a tubular insertion portion through which an axle that penetrates through the bearing is inserted; a rotor that is provided with a cylindrical portion, through which the insertion portion is inserted, and a rotation transmitter for rotating the cylindrical portion synchronously with the rotation of the wheel; a rotation detecting portion that is disposed in the housing and detects the rotation of the rotor; and a convexity that is disposed at a position that faces the inner wheel in the bearing of the rotor and capable of abutting against the inner wheel.
Furthermore, the convexities are partially disposed at positions that face the inner wheel and along a periphery of an opening through which the insertion portion is inserted.
Furthermore, a rotation detector comprises a housing one end of which abuts against a bearing that is disposed to a hub of a wheel, and which is provided with a tubular insertion portion through which an axle that penetrates through the bearing is inserted; a rotor that is provided with a cylindrical portion, through which the insertion portion is inserted, and a rotation transmitter for transmitting the rotation of the wheel to the cylindrical portion by abutting against a rotation-biasing portion disposed to the hub; a rotation detecting portion that is disposed in the housing and detects the rotation of the rotor; and a contact portion that is disposed in a portion that abuts against the rotation-biasing portion of the rotation transmitter and maintains a contact area between both members smaller.
Furthermore, the contact portion is provided with a projection that comes into contact with a flat surface of the rotation-biasing portion.
Still furthermore, the contact portion is made of a flat surface that comes into contact with the projection disposed to the rotation-biasing portion.